U.S. Pat. No. 5,703,271, filed Apr. 2, 1996, discloses a method of synthesizing multi-tier cascade polymers, as well as coating substrate surfaces, utilizing a novel family of stable trifunctionalized isocyanates. Continuing with applicants' previous work utilizing dendrimeric monomer building blocks to construct cascade polymers of predetermined internal and external architecture, applicants have begun to realize and further materialize some of the potential uses of the novel isocyanate building blocks. Previous work by applicants in forming cascade polymers were limited to the coupling of an acid (dendritic termini) and an amine. In an effort to bypass this relatively limited combination, applicants demonstrated the facile conversion of unique, sterically protected "Behera's amine" to the corresponding isocyanate by its treatment with triphogene (commercially available from Aldrich Chemical Co., catalog #33,075.2, referred to as "bis(trichloromethyl)carbonate") in the presence of triethylamine Newkome and Weis, 1996!.
The isocyanate monomers are excellent building blocks or modules for use in the transformation and introduction of surface functionality on either a cascade polymer under construction or on surfaces of substrates in general. The isocyanate based monomers also provide for rapid, iterative tier construction. That is, the layering of tiers or layers over a surface or about an existing cascade polymer can be performed relatively rapidly using the isocyanate monomers. Preliminary evaluations by applicants have demonstrated the facile reaction of Behera's isocyanate with generations 2 through 5 (8, 16, 32, 64 termini, respectively) of amine terminated, poly(propylene imine) dendrimers Worner, and Mulhaupt, 1993; deBrabander-van den Berg and Meijer, 1993! using tert-butyl alcohol as solvent. In this case, the reaction of Behera's amine isocyate building block with the poly(propylene imino) dendrimers constitutes the formation of a new dendrimer, using the dendrimers prepared as described by Worner, and Mulhaupt, as the starting core. This confirms the potential of the monomer to react with nucleophilic groups, as well as affords a reasonable insight into the reacting potential for other hindered isocyanate building blocks. Stoichiometric reactions result in the isolation of pure (95% or greater) surface modified dendrimer with no by-products. These materials can be sequentially deprotected and subjected to farther elaboration.
In view of the above, there is significant demonstration that the isocyanate based building blocks can be employed to "dendrimerize" any common material(s) possessing an acidic proton(s) or nucleophilic site(s). Examples of such substrates include silica based substances, functionalized classical linear polymers, functionalized classical micelles, microgels, spherical polymers and, as demonstrated via reaction with the poly(propylene imine dendrimers, cascade polymers. Such surface coatings or films are useful for the creation of thermally and chemically stable coatings. Thus, these coatings can be used as protective coatings on clothing, other fabrics, metal surfaces, composite-based materials, semiconducting materials or the like. Surface property modification, such as wetability, is also possible.
Biological molecules are often identified by the synthesis and screening of large collections (termed "libraries") of structures. Such methods are commonly employed with the humoral immune system, which can generate and screen some 10.sup.12 antibody molecules to identify one that specifically recognizes and binds a foreign pathogen. The development of catalytic antibodies was one of the first applications of such molecular libraries to chemistry. Other such methods have been further developed for generating and screening large populations of biological molecules in vitro for binding, catalysts or both. A large effort has been devoted towards the application of these "combinatorial libraries". Such libraries are generated by combining large numbers of precursors.
The present invention relates to the further advancement of the use of monomers normally employed in the preparation of cascade polymers and more specifically to stable multifunctionalized isocyanates in combination with combinatorial chemistry to provide novel surface layers on substrates. That is, the potential to create and utilize new materials prepared "combinatorially" is exploited by the present invention. An advancement in cascade polymer dendrimeric chemistry is derived wherein combinatorial Xiang et al., 1995! methods of dendritic construction utilize monomer mixtures possessing varying compositions of differing monomers (preferably isocyanate based monomers) for sequential tier formation.